package top.jle.spring.basic.util;

import lombok.AccessLevel;
import lombok.NoArgsConstructor;
import org.apache.commons.codec.binary.Base64;
import org.apache.commons.lang3.StringUtils;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.spec.SecretKeySpec;
import java.nio.charset.StandardCharsets;
import java.security.GeneralSecurityException;

@NoArgsConstructor(access = AccessLevel.PRIVATE)
public class AESUtil {

	/**
	 * 算法
	 */
	private static final String ALGORITHMSTR = "AES/GCM/NoPadding";



	/**
	 * base 64 encode
	 * @param bytes 待编码的byte[]
	 * @return 编码后的base 64 code
	 */
	private static String base64Encode(byte[] bytes){
		return Base64.encodeBase64String(bytes);
	}

	/**
	 * base 64 decode
	 * @param base64Code 待解码的base 64 code
	 * @return 解码后的byte[]
	 */
	private static byte[] base64Decode(String base64Code){
		return StringUtils.isEmpty(base64Code) ? null : Base64.decodeBase64(base64Code);
	}


	/**
	 * AES加密
	 * @param content 待加密的内容
	 * @param encryptKey 加密密钥
	 * @return 加密后的byte[]
	 */
	private static byte[] aesEncryptToBytes(String content, String encryptKey) throws GeneralSecurityException {
		KeyGenerator kgen = KeyGenerator.getInstance("AES");
		kgen.init(128);
		Cipher cipher = Cipher.getInstance(ALGORITHMSTR);
		cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(encryptKey.getBytes(), "AES"));
		return cipher.doFinal(content.getBytes(StandardCharsets.UTF_8));
	}


	/**
	 * AES加密为base 64 code
	 *
	 * @param content 待加密的内容
	 * @param encryptKey 加密密钥
	 * @return 加密后的base 64 code
	 */
	public static String aesEncrypt(String content, String encryptKey) throws GeneralSecurityException {
		return base64Encode(aesEncryptToBytes(content, encryptKey));
	}

	/**
	 * AES解密
	 *
	 * @param encryptBytes 待解密的byte[]
	 * @param decryptKey 解密密钥
	 * @return 解密后的String
	 */
	private static String aesDecryptByBytes(byte[] encryptBytes, String decryptKey) throws GeneralSecurityException {
		KeyGenerator kgen = KeyGenerator.getInstance("AES");
		kgen.init(128);
		Cipher cipher = Cipher.getInstance(ALGORITHMSTR);
		cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(decryptKey.getBytes(), "AES"));
		byte[] decryptBytes = cipher.doFinal(encryptBytes);

		return new String(decryptBytes);
	}


	/**
	 * 将base 64 code AES解密
	 *
	 * @param encryptStr 待解密的base 64 code
	 * @param decryptKey 解密密钥
	 * @return 解密后的string
	 */
	public static String aesDecrypt(String encryptStr, String decryptKey) throws GeneralSecurityException {
		return StringUtils.isEmpty(encryptStr) ? null : aesDecryptByBytes(base64Decode(encryptStr), decryptKey);
	}


}
